6-string banjo - restoration project

Flip

A non-musical pal recently gave me an old banjo. It's unstrung, not been looked after and very dirty. He has no interest in it and wondered if I wanted to renovate it and play or dispose of it. My interest is broadly to renovate it and return it playable and saleable to my friend.

My research has defined it as a six-string banjo made by George Matthew of Birmingham The head is dirty but undamaged. So too the fretboard and the bridge. I've come unstuck with the machine heads. They look like classical guitar units with three each side on a plate. Trouble is they're somewhat smaller than most of the classic guitar machine heads I can find online. The plate is about 102mm overall, each of the (horizontal) pegs is 25.5mm long and 6mm in diameter, with centres approximately 32mm apart.

At a pinch I might be able to renovate the existing units. There's no significant wear on the gears, the buttons are in reasonable condition and the main disfigurement is dirt. However the screws were difficult to remove despite my care so I've already committed to replacing them with new slot headed countersunk screws.

I'v bought a new set of strings and gather the tuning style is normally in a standard guitar format (EADGBE). This is despite the fact that the sixth (lowest) string has its own 'nut' at the 12 fret after which where the string disappears into the neck and emerges at the slot for the tuning pegs. I guess that means it'll be quite slack relative to the rest. I gather from a collector this string also shares a hook on the clip below the bridge with the fifth string.

If anyone can suggest where I might find new machine heads to fit I'd be grateful, at a reasonable price to match its shabby condition. Also any polite suggestion what the instrument might be worth.  

chickenbonejohn

These "zither banjos" with the tunnel thru' the neck and 6 machine heads were set up like a regular 5 string banjo, not as a 6 stringer, so one tuning peg is redundant. I've repaired a couple of them and got away with overhauling the machine heads. They are not worth a great deal, so I'd suggest fixing it up and learning to play 5 string banjo!  An alternative is to forget the tunnelled string, put a new nut and bridge on and set it up as a tenor banjo.

Flip

Many thanks @chickenbonejohn. Since writing my initial post I've realised that finding replacement under-sized 'guitar' machine heads is well-nigh impossible and I've cleaned and oiled the existing machines to reasonable condition.

Your background information is fascinating but I'm puzzled as to what the original maker/purchaser/player had in mind for the tunnel, the dinky little bone 'dot' nut for the 6th string and how it was tuned. I've bought a 6-string bridge but could easily re-use the original 5-string. I'm familiar with the object and function of zithers (and for that matter, autoharps) but what part did the shortened sixth string actually play? The position of the 'dinky dot' nut - in front of the fret closer to the head - must make the 6th string well nigh impossible to play in tune anyway? 

If I take your suggestion and set it up as a 5-string I can use the existing nut since the 6th string has a now-redundant 'dinky dot' nut of its own that i'll just ignore. In fact I have fairly podgy fingers so I'd recognised from the outset that playing six strings on a neck much narrower than any of my guitars was always going to be a challenge.

Finally, I'd been fairly sure from the outset that the instrument wasn't valuable - the quality of the veneered wood already suggested that so the idea always in the back of my mind was to return it 'prettied up' as a decoration for the pal who gave it to me (he's not musical so never considered playing it). 

chickenbonejohn

The small bone nut isn't for the 6th string, it's for the 5th string, these were NEVER strung with 6 strings. As I say, these were made with 6 machineheads (simply a pragmatic decision, as 3 a side sets were commonly available and one of the machine head is left redundant) but designed as a 5 string banjo. It seems to be a peculiarly English manner of making a 5 string banjo, as opposed to the more familiar American style with the 5th string friction tuner mounted up the neck. I have no idea where the name "zither banjo" comes from, as the instrument has nothing to do with a zither, it's a strange historical anomaly. The typical 5 string tuning is G, D, G, B, D, open G. The G which goes to the small "pip" on the neck is the high pitched drone, so it's rarely fretted and of course you'll need a proper set of banjo strings, which will be about .011, .024w, 016, .013, .011.  Here's an article about this musical misfit: https://creekdontrise.com/acoustic/zither_banjo/zither_banjo.htm